Ok, I just found this game on f-droid https://f-droid.org/en/packages/com.unciv.app/ and I have to say that it is awesome !!
I started playing one hour ago, it's smooth and I totally feel playing Civilization ... on my phone ... with a free-software ! <3 I don't know yet how the game behave when we go further in time and that there is more stuff to deal with, but for the moment I'm totally impressed. One of the best apps on f-droid in my opinion!
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.